Manufacturers of high-power components in the electric power industry measure the quality of their manufactured components by performing a variety of standard tests. One such test includes measuring the voltage discharge levels (e.g., corona levels) of a component when the component is energized and verifying that the amount of discharge is not excessive for the voltage rating of the component. Excessive corona levels may decrease the lifetime of the component or may be indicative of a problem that may lead to component failure. Another test is the basic impulse insulation level (BIL) design test. The BIL design test measures the ability of the component to handle a high voltage surge that may be comparable, for example, to the surge produced by a lightning strike. A component fails the BIL design test if the voltage surge is able to find a way to ground.
A third test is the power frequency design test. The power frequency design test measures the ability of the component to handle high voltage transients that may be comparable, for example, to the transients produced by the switching of power components.
This test is frequently conducted by exposing the component to an elevated AC voltage level typically at 50–60 Hz. A component fails the power frequency test if the elevated voltage transient is able to find a way to ground.
High-power components (e.g., high power-vacuum interrupters) may be subjected to one or more of these tests prior to sale or installation. Failure of these tests may result in an unusable component or a limitation in the use of the component.